The specific aims of Core A are to provide informatics and statistics services, of which there are four: Specific Aim 1 Human gene variant database: To maintain a database of human germline or somatic sequence variation in five enzymes involved in DNA repair and recombination: NTHL1, NEIL1-3 and RAD51 Specific Aim 2 Prediction of the functional consequences of genetic variation: To use computational methods to identify germline or somatic sequence variants having, with high probability, altered function. Specific Aim 3 Enzyme kinetics: To identify sequence variants that have altered catalytic function by designing and analyzing enzyme kinetics experiments. Specific Aim 4 l\/lutation spectrum analysis: To identify sequence variants that show alter genomic stability in cellular studies by analyzing mutation spectra. Core A services are aligned with the test of our central hypothesis, that defects in the enzyme families we study result in aberrant base excision and homology-directed repair which is the engine driving human carcinogenesis. The gene variant database and predictions of the functional consequences of genetic variation (Aims 1-2) will be used by Projects 1-3 to identify enzyme sequence variants for biochemical and cellular studies. The projects will produce data from biochemical and cellular studies, which will then be used by Core A to evaluate the consequences of genetic variation for catalysis (Aim 3, Enzyme kinetics analysis) and genomic stability (Aim 4, Mutation spectrum analysis).